Use rpm to install the kernel source code.
rpm -ihv kernel-XXX.src.rpm
Look at contents of ~/rpmbuild/kernel/ It should contain the vanilla kernel in a tarball, the .spec file, many patches, and many .config files. For me this is:
COPYING.modules linux-2.6.3-sparc-addbzimage.patch genkey linux-2.6.4-stackusage.patch kernel-2.6.8-i586.config linux-2.6.5-ext3-online-resize.patch kernel-2.6.8-i586-smp.config linux-2.6.5-ext3-reservations.patch kernel-2.6.8-i686.config linux-2.6.5-inode-clip.patch kernel-2.6.8-i686-smp.config linux-2.6.5-nostack.patch kernel-2.6.8-ia64.config linux-2.6.7-devmem.patch kernel-2.6.8-ppc32dy4.config linux-2.6.7-early-schedule.patch kernel-2.6.8-ppc64.config linux-2.6.7-hugetlb.patch kernel-2.6.8-ppc64iseries.config linux-2.6.7-i8042.patch kernel-2.6.8-ppc8260.config linux-2.6.7-i8x0-drm.patch kernel-2.6.8-ppc8560.config linux-2.6.7-iobitmap.patch kernel-2.6.8-ppc.config linux-2.6.7-might_sleep.patch kernel-2.6.8-s390.config linux-2.6.7-mlock.patch kernel-2.6.8-s390x.config linux-2.6.7-modsign-core.patch kernel-2.6.8-x86_64.config linux-2.6.7-modsign-crypto.patch kernel-2.6.8-x86_64-smp.config linux-2.6.7-modsign-ksign.patch kernel-2.6.spec linux-2.6.7-modsign-mpilib.patch linux-2.4.0-nonintconfig.patch linux-2.6.7-modsign-script.patch linux-2.4.0-test11-vidfail.patch linux-2.6.7-netdump.patch linux-2.6.0-4g4g.patch linux-2.6.7-scsi-whitelist.patch linux-2.6.0-compile.patch linux-2.6.7-symlink.patch linux-2.6.0-devmem.patch linux-2.6.7-voluntary-preemption.patch linux-2.6.0-exec-shield.patch linux-2.6.8-execshield-vaspace.patch linux-2.6.0-must_check.patch linux-2.6.8-flexmmap.patch linux-2.6.0-sleepon.patch linux-2.6.8-flexmmap-ppc64.patch linux-2.6.1-s390-compile.patch linux-2.6.8-flexmmap-s390.patch linux-2.6.2-ppc64-build.patch linux-2.6.8-flexmmap-x86-64.patch linux-2.6.2-tux.patch linux-2.6.8-print-fatal-signals.patch linux-2.6.3-crash-driver.patch linux-2.6.8-ptmx.patch linux-2.6.3-ia64-build.patch linux-2.6.8.tar.bz2 linux-2.6.3-printopen.patch linux-2.6.8-token.patch